February 15, 2011

Coastal Cities To See Rising Sea Levels By 2100

Rising sea levels could threaten an average of 9 percent of the land within 180 US coastal cities by 2100, according to new research led by University of Arizona scientists.

The Gulf and southern Atlantic coasts will be particularly affected. The cities of Miami, New Orleans, Tampa, Fla., and Virginia Beach, Va. could lose more than 10 percent of their land area by 2100.

This is the first analysis of vulnerability to sea-level rise that includes every US coastal city in the lower 48 with a population of 50,000 or more. Recent projections indicate that by 2100, the sea level will rise about 1 meter -- or even more.

Lead researcher Jeremy L. Weiss, a senior research specialist in the University of Arizona department of geosciences released a statement claiming, "According to the most recent sea-level-rise science, that's where we're heading. Impacts from sea-level rise could be erosion, temporary flooding and permanent inundation."

According to the 2000 US Census, 40.5 million people are living in and among the areas to be affected. Twenty of those cities have more than 300,000 inhabitants. Weiss and his colleagues examined how much land area from the 180 municipalities could be affected by 1 to 6 meters of sea-level rise.

Weiss, who is also a UA doctoral candidate in geosciences continues, "With the current rate of greenhouse gas emissions, the projections are that the global average temperature will be 8 degrees Fahrenheit warmer than present by 2100. That amount of warming will likely lock us into at least 4 to 6 meters of sea-level rise in subsequent centuries, because parts of the Greenland and Antarctic ice sheets will slowly melt away like a block of ice on the sidewalk in the summertime."

More than 20 percent of land in those cities could be affected with a 3 meter rise in sea levels. Nine large cities, including Boston and New York, would have more than 10 percent of their current land area threatened. With a 6 meter rise, about one-third of the land area in US coastal cities could be affected.

"Our work should help people plan with more certainty and to make decisions about what level of sea-level rise, and by implication, what level of global warming, is acceptable to their communities and neighbors," said co-author Jonathan T. Overpeck, a UA professor of geosciences and of atmospheric sciences and co-director of UA's Institute of the Environment.

Weiss, Overpeck and Ben Strauss of Climate Central in Princeton, N.J., will publish their paper, "Implications of Recent Sea Level Rise Science for Low-Elevation Areas in Coastal Cities of the Conterminous U.S.A.," in Climatic Change Letters. The paper is scheduled to go online this week.

Weiss and Overpeck had previously developed maps of how increases in sea level could affect the US coastline. Strauss suggested adding the boundaries of municipalities to focus on how rising seas would affect coastal towns and cities. For the detailed maps needed for the project, the researchers turned to the National Elevation Dataset produced by the US Geological Survey.

This higher resolution map allowed Weiss and his colleagues to identify the elevation of a piece of land as small as 30 meters on a side - the size of an average house lot.

The researchers used the USGS database to create detailed digital maps of the US coast that delineate what areas could be affected by 1 to 6 meters of sea-level rise. The researchers also added the boundaries for all municipalities with more than 50,000 people according to the 2000 US Census.

Overpeck said, "The main point of our work is to give people in our coastal towns and cities more information to work with as they decide how to deal with the growing problem of sea-level rise."

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Image 2: his map shows where increases in sea level could affect the southern and Gulf coasts of the US. The colors indicate areas along the coast that are elevations of 1 meter or less (russet) or 6 meters or less (yellow) and have connectivity to the sea. Credit: Jeremy Weiss, University of Arizona

Image 3: This map shows where increases in sea level could affect New Orleans, Virginia Beach, Va., Miami, Tampa, Fla., New York and Washington, D.C. The colors indicate areas along the coast that are elevations of 1 meter or less (russet) or 6 meters or less (yellow) and have connectivity to the sea. Credit: Jeremy Weiss, University of Arizona